Disc drives are common data storage devices. A typical disc drive includes a rigid housing or deck that encloses a variety of disc drive components. The components include one or more discs having data surfaces coated with a medium for storage of digital information in a plurality of circular, concentric data tracks. The discs are mounted on a spindle motor that causes the discs to spin and the data surfaces of the discs to pass under respective hydrodynamic or aerodynamic bearing head sliders. The sliders carry transducers, which write information to and read information from the data surfaces of the discs.
In disc drives, magnetic spacing can be defined as the spacing between the transducers and the data surfaces of the discs. In high recording density hard drives, it can be beneficial for the magnetic spacing to be adjustable for the pole tip of a transducer to stay very close to the media without crashing the slider. This adjustment also enables compensation for pole tip thermal expansion.
Proposed approaches to achieving adjustable magnetic spacing include utilizing a shape memory alloy (SMA) on the suspension, utilizing a bimetal gimbal, and electrostatic actuation. The SMA concept places a piece of shape memory alloy on the suspension arm to adjust the preload force as the temperature changes. The bimetal gimbal approach bends the gimbal by heating up one layer of the gimbal such that the pitch angle is adjusted. Both approaches are suitable for low frequency control of the magnetic spacing between the pole tips and the disc, but not for high frequency control because thermal actuation is a relatively slow process. The electrostatic approach adjusts the magnetic spacing by applying potential between the head and the disc to form a capacitor. It has a high probability of crash (“snap over”), but the bandwidth is relatively high compared to SMA and bimetal gimbal approaches. None. of these approaches render an optimum high band width magnetic spacing control.
Embodiments of the present invention address one or more of these and/or other problems, and offer other advantages over the prior art.